In order to maintain and/or increase a product yield in a line for manufacturing a semiconductor substrate, a thin-film substrate, or the like, inspection is performed for a defect present on the surface of the semiconductor substrate, the thin-film substrate, or the like. As prior-art defect inspection techniques, Patent Literature 1 (JP-A-9-304289), Patent Literature 2 (JP-A-2006-201179), Patent Literature 3 (U.S. Patent Publication No. 2006/0256325), and so on are known. These are the techniques in which illumination light is focused into dimensions of several tens of μm on the sample surface to detect a minute defect, light scattered by the defect is collected and detected, and the defect of dimensions equal to or more than a range of several tens of nm to several μm is inspected. By moving a stage which holds a sample (an inspection target) thereon rotationally and translationally, an illumination spot is spirally scanned on the surface of the sample, whereby the full surface of the sample is inspected.
In the Patent Literature 1 and 2, there are described techniques for detecting components of light scattered by a defect emitted at a high angle and emitted at a low angle, and classifying a type of the defect depending on their ratio.
Further in the Patent Literature 2, there is described a technique for calculating dimensions of the detected defect based on an intensity of light scattered by the defect.
Also, in the Patent Literature 3, there is described, in order to reduce thermal damage applied to a sample, controlling a power of illumination light, a scan speed of an illumination spot, or dimensions of the illumination spot while inspecting an inspection target. More specifically, it is described that the thermal damage applied to the sample is assumed to be determined by a product of an illumination power density and an irradiation time and, in order not to make it exceed a certain value, the power of the illumination light, the scan speed of the illumination spot, or the dimensions of the illumination spot are varied according to a radial position on the sample while scanning.
As a technique for inspecting a sample in a short time by illuminating a large area of the sample surface with a Gaussian beam elongated in one direction and detecting an illumination area at once using a detector with a plurality of pixels such as a CCD, Patent Literature 4 (U.S. Pat. No. 6,608,676) is known.
As a technique for shaping illumination light into a shape that a plurality of illumination spots are arranged on the surface of an inspection target using an aspherical lens or a diffractive optical element in oblique incidence illumination, Patent Literature 5 (U.S. Pat. No. 7,385,688) is known.